1. Technical Field
The disclosure relates in generally related to a semiconductor device and the method for fabricating the same, and more particularly to a semiconductor device with memory cells, logic elements and high-voltage elements, as well as the method for fabricating the same.
2. Description of the Related Art
An non-volatile memory (NVM) device which is able to continually store information even when the supply of electricity is removed from the device containing NVM cells has been widespreadly adopted by bulk solid state memory applications in the art. Because the process for fabricating the NVM device offers good compatibility with the silicon integrated circuit (IC) process, the NVM device is thus usually integrated with complementary metal oxide semiconductors (CMOSs) to form an embedded memory device, a silicon IC device including at least one NVM device (such as a flash memory cell), at least one logic element (such as a MOS transistor) and other semiconductor device (such as a high-voltage transistor) integrated on a substrate.
Conventionally, in order to reduce the manufacturing cost, etching steps using identical reticles for etching polysilicon may be utilized to form the gate electrodes of the logic element and the high-voltage transistor on a substrate, during the process for fabricating an embedded memory device. Another reticle is then adopted to form the word lines of the NVM device integrated on the same substrate. However, since the reticle that is merely prepared for forming the word lines of the NVM device has lower transmission rate (RT), thus it is more difficult to control the etching steps to stop at a desired etching, in comparison with the process prepared for forming the gate electrodes of the logic element and the high-voltage transistor. As a result, problems either in over etch or otherwise in excess etch residue may occur due to lack of process window.
Furthermore, there are other problems faced by the conventional approaches. Because the electrodes of the logic element and the high-voltage transistor that are formed by the same etching steps using identical reticles have the same thickness, additional ion implantation processes, such as tilt ion implantation or/and doping process for forming a guard ring, may be required to make the high-voltage transistor to reach a predetermined breakdown voltage. The process window of the embedded memory device could be further reduced by the needed ion implantation processes.
Therefore, there is a need of providing an improved semiconductor device and the method for fabricating the same to obviate the drawbacks encountered from the prior art.